What benefit does striking some random target hundreds of miles within Russia accomplish for Ukraine, who is slowly losing the ability to hold ground?

The goal of the Ukraine conflict is to create a Pyrrhic victory for Russia so costly that it collapses from within. Long range missiles capable of destroying key domestic infrastructure and material reserves will (hypothetically) hasten that economic collapse.

If you can start hitting major financial centers, administrative offices, and social meeting spaces, you might even be able to decapitate some of the senior leadership and kick off a succession crisis in Putin’s government. Alternatively, you push these leaders so far down into hiding that they can no longer effectively govern the country and foreign-sponsored insurgents can take over.

That’s the theory of the war, at least. In practice, NATO leadership is still unsettled by the prospect of a Total War with a nuclear armed state. So they’re not quite ready to drop a long range cruise missile on the Frunzenskaya Embankment, for fear of what a retaliatory strike would look like.